The invention relates to marine propulsion devices, and, more particularly, to marine propulsion devices including a drive shaft housing which supports an engine, and an exhaust housing located within the drive shaft housing and connected to the engine.
A typical outboard motor includes an engine, a drive shaft housing, an adaptor to which both the engine and the drive shaft housing are connected and which is sandwiched between the engine and the drive shaft housing, and an exhaust housing connected to the lower face of the adaptor and extending within the drive shaft housing. This arrangement provides a joint between the engine and the adaptor, a joint between the adaptor and the drive shaft housing, and a joint between the adaptor and the exhaust housing. Typically, cooling water for the engine is pumped upwardly through the adaptor and is pumped upwardly to the adaptor either through a conduit located inside the drive shaft housing and outside the exhaust housing or through a passageway inside the exhaust housing.
It is known to tune the exhaust of such an outboard motor by providing the exhaust housing with a specially constructed exhaust passage. See, for example, Holtermann, et al. U.S. Pat. No. 4,337,054. Furthermore, it is known to provide such an outboard motor with an idle exhaust relief system that discharges exhaust gases above the water level when the outboard motor is operating at idle or low speeds.
Attention is directed to the following U.S. Patents:
______________________________________ Inventor U.S. Pat. No. Issued ______________________________________ Scharpf 4,660,378 April 28, 1987 Holtermann 4,337,054 January 29, 1982 Ziegler 3,772,887 November 20, 1973 Boerma 3,695,238 October 3, 1972 Miller 3,692,006 September 19, 1972 Hulsebus 3,045,423 July 24, 1962 Larsen 3,198,162 August 3, 1965 Gazzara 3,282,373 November 1, 1966 Hoiby et al. 3,296,997 January 10, 1967 Kollman 3,310,022 March 21, 1967 Boda et al. 3,350,879 November 7, 1967 Miller 3,520,270 July 14, 1970 Tado 3,577,952 May 11, 1971 Miller et al. 3,911,852 October 14, 1975 Harralson et al. 3,967,446 July 6, 1976 Maier et al. 4,036,162 July 19, 1977 Harbert 4,019,456 April 26, 1977 Harada 4,145,988 March 27, 1979 Sanmi et al. 4,303,401 December 1, 1981 Sanmi et al. 4,354,849 October 19, 1982 Nakahama 4,421,490 December 20, 1983 Hall et al. 4,507,092 March 26, 1985 Price 4,589,852 May 20, 1986 Taguchi 4,604,069 August 5, 1986 Okazaki 4,607,723 August 26, 1986 Freund et al. 4,668,199 May 26, 1987 ______________________________________
Attention is also directed to the following Japanese patent applications:
______________________________________ Appl. No. Filed ______________________________________ 54-25059 March 6, 1979 55-133541 September 25, 1980 55-155500 November 5, 1980 55-156562 November 7, 1980 57-68908 April 24, 1982. ______________________________________